This invention relates primarily to providing a new method of cushioning the impact of vehicle occupants with the interior of the vehicle during an accident. Any interior surface except windows, which can be impacted by an occupant's head, chest, knees, thighs, shoulders, or any other portion of the body, would be a candidate for application of the improved padding which is the subject of this invention. Of particular interest is the application of this improved padding to vehicle doors, knee bolsters and headrests. Other applications would be for windshield headers, "A" pillars, "B" pillars, instrument panels, the interior vehicle roof, and seats.
Side impacts are responsible for one-third of the serious injuries sustained by occupants in automobiles involved in crashes. The majority of these traffic accidents involve other automobile or light trucks. In most cases of interest, the target vehicles are struck at angles which are within 30 degrees of orthogonal and on the driver side..sup.1 FNT .sup.1 "Results of the National Highway Safety Administration's Thoracic Impact Protection Research Program", by J. R. Hackney, M. W. Monk, W. T. Hollowell, L. Sullivan, D. T. Wilke, SAE Paper 840886, May 1984.
Data collected by the National Accident Sampling System (NASS).sup.2 provide a basis for ascertaining the extent of injuries to automobile occupants in side impacts. Based on police reported accidents in 1985, 29% or 1,186,000 of the 4,067,000 occupants of cars and light trucks involved in motor vehicle accidents were in collisions involving side impact. 28,000 of these occupants sustanined serious (AIS.gtoreq.3) injuries. The Fatal Accident Reporting System (FARS).sup.3 provides another estimate of the relative significance of side impacts. In 1986, 24,833 fatalities occurred in passenger cars. Of these fatalities, 6,942 or 28% occured in situations where side impact was the principal impact and the vehicle did not overturn. FNT .sup.2 National Accident Sampling System, 1985. "A Report on Traffic Accidents and injuries in the United States", National Highway Traffic Safety Administration, DOT-HS-807-074, Feb. 1987. FNT .sup.3 FARS 1986 Database, National Highway Traffic Safety Administration.
The percentage of occupants injured or killed in side impacts is likely to increase now that air bag restraint systems are being widely adopted to protect occupants in frontal impacts. The National Highway Traffic Safety Administration (NHTSA) of the Department of Transportation is currently considering imposing regulations which will require protection of occupants in side impacts.
In a typical side impact, a "bullet" or striking car impacts the "target" or struck car. The bumper of the bullet car causes the door of the target car to intrude into the passenger compartment where it impacts the occupant causing injury. If the target vehicle door is weak and the front structure of the bullet car is strong, the door will impact the occupant at approximately the speed of the bullet vehicle. If, on the other hand, the target car has a strongly reinforced door and the bullet car a soft front structure, significantly less intrusion will take place and the impact between the door and the occupant will take place at a velocity which is equal to the bullet car velocity times the mass of the bullet car divided by the sum of the masses of the bullet and the target car. This is called the "momentum velocity". For impacts between vehicles of approximately equal weight, the velocity of impact between the occupant and the door for this second case would be approximately one-half of the bullet car's velocity. The first step, therefore, to reduce the injuries in side impacts is to reinforce the side structure and soften the front structure of vehicles. In frontal impacts, a vehicle typically strikes a rigid object such as a tree, pole, barrier or another car traveling in the opposite direction. The velocity change of the vehicle, therefore, is frequently close to the actual velocity of the vehicle. In side impacts, the typical accident is one car impacting a second car where the velocity change is approximately one-half of the impacting vehicle's velocity. The average velocity change in side impacts, therefore, is approximately one-half of the average velocity change in frontal impacts.
Experimental data of Dargaud and Bourdillon.sup.4 on 30 MPH car-to-car side impacts show that .DELTA.V of the struck vehicle is approximately the same as the maximum intrusion velocity of the side door at time of contact with the occupant. Their data show that for 30 MPH side impacts, the maximum door intrusion velocity is about 18 MPH. Hardy.sup.5 also reported similar results. FNT .sup.4 Dargaud R., and Bourdillon, T., Simulation of Lateral Impact with Mobile Deformable Barrier. SAE Technical paper No. 860051, 1986. FNT .sup.5 Hardy, R. N., Simulations to Assess the Influence of Car Lateral Impact Characteristics on Occupant Kinematics. College of Aeronautics Report No. 8428, Cranfield Institute of Technology, Bradford, England, 1984.
Air bag systems have been designed for use in protecting occupants in side impacts. These systems work well; however, since the severity, as measured by the occupant velocity change, of side impacts is substantially less than for frontal impacts, air bag systems may not be necessary. In fact, as will be demonstrated below, as little as six inches of padding can provide excellent occupant protection for side impact velocities as high as 30 miles per hour.
Padding has additional advantages over air bag systems. Padding is always in place with nearly 100% reliability. Air bags, on the other hand, are deployed when a certain threshold speed is exceeded which is generally chosen to protect occupants in more severe cases. Therefore, the occupant in the air bag case will receive more injuries at impacts below the chosen threshold. Air bags are considered supplemental to seat belts for frontal occupant protection. In side impacts, however, the occupant sitting on the struck side of the vehicle does not receive protection from a seat belt. He is therefore much more likely to be injured in a side impact accident, especially below the chosen threshold, than an occupant wearing a seat belt in a below threshold frontal impact. Finally, the cost and complexity of side impact air bag systems greatly exceeds that of the padding systems described in this invention.
If an air bag is deployed in a side impact accident, it must be replaced. In contrast to frontal impacts, where the vehicle is totaled in most accidents severe enough to require an air bag, the vehicle in a side impact accident is frequently repaired. Thus, if a side impact air bag system is used, it would have to be replaced after an accident adding significantly to the vehicle repair cost. In most cases, the padding described in this invention would reset itself to its undeformed state and thus would be immediately available to absorb a second impact. In contrast, once a side impact air bag has deployed and deflated, no additional protection is available to the occupant should a second impact take place.
The design of knee bolsters has not received as much attention from air bag system designers as it deserves. In the case of the unbelted occupant, as taught by Brantman and Hatfield in U.S. Pat. No. 4,721,329, the knee bolster must absorb the kinetic energy of the lower torso of the occupant which is typically about one-half of the occupant's total kinetic energy. A properly designed knee bolster should also guide the knees to aline the femurs with the direction of force and minimize the tendency of the knees to slip off the knee bolster. Finally, since at the end of the accident, an air bag typically contains pressurized gas which propels the upper torso back toward the seat, the knee bolsters should also simultaneously propel the lower torso back into the seat. If this is not done, there is a possibility of neck injury due to the impact between the driver's head and the seat.
The padding system described in this invention, in addition to providing protection in side impacts also results in a highly efficient knee bolster design satisfying all of the above criteria. In addition, this knee bolster is available for protection in lower speed accidents where the air bag did not deploy and will reset itself in below threshold accidents.
The padding of the present invention can also be applied to headrests. Headrests are mainly useful to prevent hyperextension neck injuries to occupants in rear impacts. The padding of the present invention permits the design of headrests which have the minimum weight and the maximum injury reduction potential.
Vehicle doors, knee bolsters and headrests are three of many applications of the padding disclosed in this invention as will be described in detail below.